The invention relates to a spray device and, more particularly, a spray device for a paint booth for car bodywork.
To paint motor vehicle bodywork, a coating product is sprayed in liquid or powder form onto the bodywork. To avoid sprays of the product from being sprayed outside of the painting zone, the bodywork is conveyed into a tunnel-shaped booth equipped with an air lock and ventilated from the top downwards. Inside this booth there are sprayers which send a coating product, particularly paint, onto the bodywork that is to be painted.
In order to disturb the atmosphere within the booth as little as possible and to avoid various dirt which gives rise to defects in the form of inclusions in the painted parts, it is known practice for the motor elements needed for spraying coating onto the bodywork to be placed outside the booth in an attempt to leave only the sprayers inside the booth. Thus, document FR-2 710 858 describes a machine for applying paint comprising a system of overlapping curtains allowing only the sprayer and the arm supporting it to be placed inside the booth while the other mechanical parts are placed outside the booth. That makes it possible to limit the cleaning operations to the sprayer and its support arm, and to the relatively smooth walls of the booth and of the overlapping curtains.
The disadvantage with such a machine is, however, its bulk both in the longitudinal direction, that is to say in the direction of the axis of the conveyor on which the bodywork moves and also in the transverse direction. Indeed conventionally, a booth for applying paint comprises three lateral machines on each side of the conveyor and one machine intended to spray coating product onto the upper parts of the bodywork. In order to be able to save on the cycle time taken to paint a bodywork and in order to be able to paint the bodywork parts situated transversely to the axis of the conveyor, such as the fronts and the rears from a constant distance, the machines have a degree of freedom, generally known as the track, parallel to the axis of the conveyor. In the case of lateral machines, the xe2x80x9ctrackxe2x80x9d is generally about 600 to 800 mm. These machines therefore have a relatively long length in the direction of the axis of the conveyor.
In addition, it is necessary to leave a sufficient gap between two machines so as to avoid the sprayers painting each other. A distance generally observed between two sprayers is 1100 mm. It is also necessary for the operators responsible for the paint booth to be able visually to check the application of paint to the bodywork. For that, a sufficiently large glazed area needs to be provided between two adjacent machines.
All of these constraints mean that the booths have a relatively long length with respect to the axis of the conveyor. Likewise, the construction of the machines of the prior art entails the need to have an axis of penetration transversal to the axis of the conveyor with sufficient travel to be able to follow the curvature of the bodywork and also to be able to adapt to suit bodywork of different widths. The machine thus has a transverse travel which entails increasing the depth of the structure of the machines. This then yields a mechanical part of relatively great width on the outside of the booth.
On the whole, paint booths and associated machines have a relatively great length and width with respect to the axis of the conveyor. With a view to reducing the operating costs, particularly the costs associated with the air flow and the cleaning costs, it is important to reduce both the length and the width of the equipment alongside a conveying line through a workshop. This is because each square meter of workshop represents a substantial investment and an annual operating cost which are of course passed on to the cost of the end product.
Document FR-2 777 483 proposes arrangements that make it possible to reduce the number of sprayers in a complete station for spraying coating product by proposing a method of spraying coating product which, in practice, makes it possible to have just two lateral application machines instead of the three machines usually used. What happens is that as the production rates often vary rapidly with the demand, adaptation is achieved by increasing the number of sprayers linearly with relation to production:
3 up to 2 m/min,
7 from 2 to 3.5 m/min,
9 above that.
However, this solution entails including tracks in the lateral machines and this, at the end of the day, does not make it possible to reduce the width of the complete painting station.
Another disadvantage of the application machines described hereinabove is their lack of flexibility. Motor manufacturers are increasingly wanting to have the ability to manufacture any model in their range on any given assembly line. Likewise, when a new model comes out, the style of which may lead to zones which are more difficult to access for painting, the manufacturer wants to be able to keep his painting installations that he used for the older models. Now, in the case of the conventional machines as described hereinabove, the points that the kinetics of the machine can access are limited, and it can no longer be guaranteed that it will be possible to paint the new vehicles without requiring touch-ups.
Likewise, the speeds of the conveyor transporting the bodywork are constantly increasing with a view to making the production tooling even more profitable and thus to reducing the final cost of the manufactured product. This increase in the speed of the conveyors in the current state of the art involves increasing the track lengths of the machines that apply the protective coating. To increase this track in machines of the prior art it is then necessary to increase the length along the axis of the conveyor of the application stations and this goes against the search for economy set out above.
An installation as described hereinabove obviously comprises numerous control and measurement members which are generally grouped together into a series of electro-pneumatic cabinets situated around the spray booth. These members may just as easily be placed in a unit fixed to the back of each machine as disclosed in patent EP-B1-0618013. In both instances, this leads to the occupation of additional floor space and therefore to more expensive investments.
To spray a coating product onto a car bodywork or the like, it is also known practice to use robots. Patent U.S. Pat. No. 4,984,745 discloses such a robot which comprises a fixed base on which is mounted to pivot, about a vertical axis, a rotating base. The latter carries an articulated arm equipped at its free end with a wrist bearing a sprayer.
Such a robot allows a bodywork to be tracked on a conveyor over a greater distance than the machines described earlier.
However, such a robot has numerous disadvantages. Specifically, the robot is placed almost entirely in the spray booth. Problems of deposits on the entire robot, not only the arm supporting the sprayer but also the fixed base and the moving base are then encountered. This poses problems as regards the cleaning of the installation, which takes a relatively long length of time and generates bodywork defects in the form of inclusions.
Another disadvantage with these robots is that they are placed at the end of the conveyor and that their bulk in the widthwise direction, that is to say transversely to the axis of the conveyor, is relatively great. This bulk is of the order of 20% greater than that of the machines described above, and the booth is therefore more expensive to operate both in terms of energy and from an ecological standpoint.
The invention provides a device for applying a coating product that makes it possible to produce an application station which has a small floor space occupancy. As a preference, this device will have a long track length, great flexibility and will comprise machines placed essentially outside the application booth.
To this end, the present invention proposes a device for spraying a coating product intended in particular for a paint booth for spraying car bodywork, comprising a moving arm able to perform a tracking movement tracking the object that is to be coated, which is moving in a horizontal plane along a conveyor or the like, and at the free end of which a sprayer is placed.
The pivoting arm is mounted on a base which can be given a rotational movement about an axis that is roughly horizontal and roughly perpendicular to the axis of conveying. Furthermore, in order to be able to provide the tracking movement, another degree of freedom is needed. In a first form of embodiment, this degree of freedom is given by a translation along an essentially vertical or horizontal axis of the rotary base carrying the arm and, in another embodiment, this degree of freedom is given by virtue of the presence of an articulation forming an elbow on the arm carrying the sprayer.
When the device comprises an articulated arm, the base may also be moved in translation in a vertical or horizontal direction. The device then has an additional degree of freedom. This configuration makes it possible simply to increase the flexibility of the machine still further, allowing it to reach remoter points.
As a preference, a wrist is mounted between the free end of the arm and the sprayer. In this case, the wrist has, for example, two degrees of freedom and can rotate, on the one hand, about a longitudinal axis with respect to the arm or to that part of the arm which carries it and, on the other hand, about an axis inclined about this longitudinal axis. For example, the angle of inclination of this axis is of the order of 45xc2x0.
For a device according to the invention comprising an articulated arm with an elbow, the axis of the elbow is advantageously parallel to the axis of pivoting of the arm on the base.
The present invention also relates to an installation for spraying parts, particularly car bodywork, which comprises at least one spray device as described hereinabove.
Such an installation comprises, for example, on each side of a conveyor, two spray devices as described hereinabove with five degrees of freedom and one spray device according to the invention comprising six degrees of freedom.
To limit dirtying, which makes it possible to avoid defects in the form of inclusions in the painted bodyworks, and to reduce cleaning times to a minimum, the installation advantageously comprises a wall passing more or less level with the face of the base carrying the articulated or unarticulated arm of a device according to the invention, the axis of pivoting of the arm on the base being placed with respect to the wall inside the installation, that is to say on the conveyor side.
Thus, it is possible in such a machine to conceive of a location that allows the control and measurement members to be sited. This location may be incorporated directly into the structure of the machine without appreciably increasing its volume. This then yields a machine which has a track far longer than that of the machines of the prior art and that incorporates its own electric control cabinet in a volume equivalent to that of the machines of the prior art.